Water-tube boiler



April 29, 193% t A. w. PATTERSON, JR y WATER TUBE BOILER Filed July 5, 1927 I N V EN TOR.

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Patented Apr. 29, 1930 PATENT orrics ARTHUR W. PATTERSON, JR., OI ROSELLE, NEW JERSEY WATER-TUBE BOILER.

Application filed July 5, 1927. Serial No. 203,402.

This invention relates to water tube boilers of the so-called vertical type. Boilers of this type have tubes extending between upper and lower drums in an up and down direction which may be vertical or considerably off the vertical. The tubes are usually arranged in two or more sets or banks, and there is'usually a single lower drum and one, two or three upper drums. It has been the practice for years to baflie boilers of this ty e by means of battle plates or partitions e tending longitudinally of the tubes. More recently these boilers have to same extent been provided with crossbaflies, that is, bafiies which wholly or partly extend transversely'of the boiler tubes, and such cross-baffling results in more efficient boiler operation.

The advantage of back arch firing in securing high ratings and efiiciencies in boiler operation has long been recognized, and back combustion arches are now generally applied to modern high power boilers in connection with chain grate stokers or mechanical under-fed stoker grates where this can be done without involving undesirable changes inthe furnace construction or setting of the boiler to provide the necessary room for the back arch. With vertical boilers, the change to back arch construction while retaining the existing longitudinal baffle construction, has involved considerable difliculty and expense because of the necessity of either raising the boilers or lowering the furnace floor in order to avoid blanking the lower portions of the front boiler tubes.

The object of the present invention is to avoid these difficulties in the application of back arch firing to vertical boilers and to 40 provide a construction such that the advantages of back arch firing may be obtained without'substantial change in the boiler setting: that is, without the necessity of raising the boiler 01'' of, lowering the furnace floor. These objects are attained by providing, in connection with a cross-baffled boiler, a back arch located close to the front tubes or front bank of tubes of the boiler with the upwardly extending covering wall of the arch meeting the front edge of the upper cross-baiiie. By this arrangement, a back arch furnace with the necessary open space above the front portion of the grate approved embodiments of the invention, and

such a description will now be given in connection with the accompanying drawings, in which:

Fig. 1 is a sectional view, somewhat diagrammat c, of a vertical boiler of well-known construction, provided with cross-bafiles and a back arch furnace in accordance with the inventlon. Fig. 2 is a similar view of a portion of a boiler such as shown in Fig. l, but showing a slightly modified arrangement of the back are The furnace shown in Fig. 1 contains a water-tune boiler of well-known form having a lower drum 10, a plurality of upper drums 11, 12 and '13, and a plurality of sets of tubes 14, 15 and 16 extending upward from the lower drum, one set extending to each of the upper drums. Extending in front of the lower drum and in front of the-lower portion of the front set or bank of tubes 14, is a fire box 17 having an opening provided with a feed hopper 18 at its front. Projecting through this opening and extending the length of the fire box, is an inwardly moving chain grate 19. A front arch 20 extends over the front portion of grate at suflicient distance above the grate to provide a mixing space 21 over the front portion of the grate. A back arch 22 lower than the front arch 20 extends forwardly over the rear portion of grate and has an upwardly extending portion, or covering wall, 23 which extends rearwardly and upwardly from the front end of the arch to about the middle of the front bank of tubes 14. This wall 23 forms with the rear end of the front arch a restricted mixing passage'24 leading from the mixing space 21 to the upper pass of the boiler. The back arch, as shown in this figure, is completed by a wall 25 of arch material extending from the upper end of the wall 23 downwardly to the arch supporting abutment 26.

A cross-bathe 30 extends from the top of the back arch, that is, from the upper end of the wall 23, transversely across the first and second banks 14 and 15 of boiler tubes. A second bafiie has a portion 31 extending downwardly from the drum 13 longitudinally of the tubes at the rear side of the rear bank of tubes 16 and a portion 32 extending transversely across the sets of tubes 16 and 15 below the bafiie 30. The baflies thus provide an upper passageway across the upper portions of the sets of tubes 14 and 15, to the upper portions of the tubes 16 where the gases turn downwardly, a second pass for the flow of combustion gases forwardly from the upper portions of the tubes of the set 16 past the intermediate portions of the sets 15 and 14, and a lower pass for flow backwardly past the lower portions of the tubes of all three sets. The gases then pass upward and out through the out-let or stack flue 33.

It is to be understood that the furnace may be provided with the usual or any suitable means for introducing air under the grate 19 and beyond the inner end of the grate with the greater volume of air flowing through the rear portions of the grate, so that combustion will take place with the usual advantages of a back arch furnace having a grate by which the fuel is given a continuous inward or backward movement. rising from the front portion of the grate will be largelythe products of incomplete combustion, while on the rear portions of the grate, through which the larger proportionate amount of air passes, intense combustion will take place; and the hot products of com bustion with excess air rising from this portion of the grate and deflected forwardly by the over-hanging back arch will meet in the space 21 with the fuel gases from the front portion of the grate and thorough mixing of the gases will result in very complete combustion, thorough mixing being further aided by providing the constricted passage 24, this passage also serving to distribute the gases over the tubes. The combustion gases in flowing through the upper pass of the boiler will be brought immediately in contact with the upper portions of the boiler tubes where the greatest heat is desirable.

It will be noted that the back arch, extending forward in front of the lower boiler drum 10 and meeting at its upper part the front edge of the upper cross-battle 30, does not require any lowering of the grate from the position which it would otherwise occupy, or any raising of the boiler. The arrangement of the furnace with the back arch gives all The gases the advantages of back arch firing of larger furnace volume, better mixture of the gases and more complete combustion, with increased capacity and efliciency. The crossbafiling of the boiler provides a passageway for the gases of combustion of gradually decreasing cross-section corresponding approximately to the decreased volume of gas due to shrinkage in cooling, so that the velocity of the gases is thus maintained substantially constant or speeded up somewhat, the efliciency of the boiler being thereby improved.

When the space available within the furnace permits, it is usually desirable to complete the back arch as shown in Fig. 1. In some cases, however, and especially where the space for receiving the arch supporting means is limited, a longitudinal baflie 35 on the first row of tubes of the front set may be employed for sealing the space back of the arch as shown in Fig. 2, the upper crossbaflle then contacting with and extending past the upper end of this longitudinal baflie and being footed on the upper end of the arch as shown.

What is claimed is:

1. The combination with a water tube boiler of the Sterling type having a lower drum and a plurality of upper drums and tubes connecting said drums, of a furnace having a fire box extending in front of the lower drum, a back combustion arch extending from a point adjacent the lower drum forwardly over the rear portion of the firebox and then rearward and upward to a point adjacent the intermediateportion of the front tubes, a cross baflie extending from the top of the back arch transversely of the tubes in the same general direction as the upper face of said portion of the back arch which extends rearward and upward, and a second battle having a section spaced below said cross baflie and extending transversely of the tubes and another section extending upwardly from the end of said section longitudinally of the tubes to the rear drum.

2. The combination with a water tube boiler of the Sterling type having a lower drum and a plurality of upper drums and .tubes connecting said drums, of a furnace having a firebox extending in front of the lower drum, a back combustion arch extending from a point adjacent the lower drum forwardly over the rear portion of the firebox and then rearward and upward to a point adjacent the intermediate portion of the front tubes, a cross bafiie also extending upward and rearward from the top of the back arch and forming in effect a continuation of the portion of the back arch which extends upward and rearward, and a second baflle having a section spaced below said cross bafile and extending transversely of the tubes and another section extending upwardly from the end of said section longitudinally of the tubes to the rear drum.

3. The combination with a water tube boiler of the Sterling type having a lower drum and a plurality of upper drums and tubes connecting. said drums, ofa furnace having a firebox extending in front of the lower drum, a back combustion arch extending from a point adjacent the lower drumforwardly over the rear portion of the firebox and then rearward and upward to a point adjacent the intermediate portion of the front tubes, a front arch lying above the forward end of the furnace with its rear end extending to a point above and adjacent said rearwardly and upwardly extending portion of the back arch to provide a restricted passage for the gases of combustion, a cross bafile extending from the top of the back arch .trans-' versely of the tubes in the same general direction as the upper face of said portion of the back arch which extends rearward and upward, and a second baflle having a section spaced below said cross bafile and extending transversely of the tubes and another section extending upwardly from the end of said section longitudinally of the tubes to the rear drum.

In testimony whereof I have hereunto set my hand.

.ARTHUR W. PATTERSON, JR. 

